Dehydrogenation process



United States Patent The present invention relates to processes for the dehydrogenation of hydrocarbon materials. More particularly, it relates to the preparation of hydrocarbon materials. More particularly, it relates to the'preparation of hydrocarbon materials of greater unsaturation than the starting materials from which they are produced. Specifically, it is concerned with the conversion of aliphatic, saturated or olefinic unsaturated, hydrocarbons "into monoand poly-olefinic compounds corresponding thereto. Specifically included within the scope of the invention is a dehydrogenation process for the conversion of butane or butenes into butadiene.

Processes for the dehydrogenation of hydrocarbons by means of reactions involving the use of iodine in connection therewith are now known in the art. Moreover, it is known that hydrogen iodide formed during the course of the reaction may be reconverted into iodine in the reaction zone, through the use of oxygen. Processes in volving the foregoing reactions are generally accomplished by passing a mixture of components in the gas bene from "toluene.

3,205,280 Patented Sept. 7, 1965 .jce.

going reactions are illustrated by the following examples hexane, toluene from n-hep-tane; naphthalene from bu'tyl cyclohexane; diallyl from propene; and dibenzyl and stil- In certain instances the dehydrogenation is also accomplished by other reactions such as, for example, isomerization, dealkylation, and exchange of hydrogen atoms or alkyl groups between dilferent hydrocarbon molecules.

The process of the invention is applicable generally to hydrocarbons having two or more carbon atoms in the molecule. Starting materials which are particularly suited are those aliphatic hydrocarbons having a carbon chain of four C-atoms in the molecule, for example, nbutane, 1- and Z-butene, or isopentane. It is often advantageous to employ mixtures of paraflins with the cone spending olefins, such as certain refinery fractions which consist predominantly of n-butane' and the butenes. Us-

phase through a reaction zone which is maintained at elevated temperatures.

Theme of inert contactmaterials, such as, for example, glass beads, quartz chips,

and the like, is also well known.

Additionally, the art teaches the use of various heavy metal oxides as suitable catalysts for the dehydrogenation of hydrocarbons, particularly when halogens are absent. Furthermore, it is known to employ catalysts which contain, in addition thereto, an oxide of an alkali or alkaline earth metal, as for example, Fe O with K 0.

However, while the art is rather voluminous with regard to catalytic conversions of olefins' to diolefins, there remains considerable interest in and need for catalytic processes involving the dehydrogenation of saturated organic material such as paraflinic hydrocarbons. In addi-- tion to disclosing a process for such conversion, the present invention also sets forth means whereby parafiinic andolefinic hydrocarbons may be dehydrogenated in appreciably greater yields than has heretofore been accomplished.

In accordance with the present invention, a paraflinic or an olefinicially unsaturated hydrocarbon or a mixture thereof is dehydrogenated by a process which comprises contacting the hydrocarbon feed in the vapor phase and in admixture with oxygen and a halogen with a solid catalyst comprising an alkali metal or alkaline earth metal compound.

. The'present invention therefore provides for the production of alkenes from alkanes, as well as the production of alkadienes and alkapolyenes from both alkanes and alkenes. Also it has been found that alicyclic hydrocarbons undergo similar conversion to cyclic olefins and/or aromatics. The removal of hydrogen atoms is often accomplished by the formation of new bonds between carbon atoms originally not connected with each other. Thus, an acyclic hydrocarbon may be transformed into a carbocyclic compound, as, for example,

ually it is advisable to recycle those hydrocarbons which either have not, or have only partly been converted in one pass. Thus, in the preparation of butadiene from butane and/or the butenes, the unconverted compounds are passed again into the reactor, together with new feed, after having recovered butadiene from the stream of products leaving the reactor.

In carrying out the process of the invention the gaseous mixture of the hydrocarbon is dehydrogenated by passing it with oxygen and a halogen over a suitable solid catalyst. Instead of pure oxygen a molecular oxygen containing gas, such as air, is usually preferred. The

. amount of oxygen to be applied depends in general upon the hydrocarbon which is to be dehydrogenated and also on theparticular product which it is desired to prepare preferentially. In other words, approximately stoichiometric amount of oxygen should be employed in theory, in accordance with the number of hydrogen atoms which are to be removed from the hydrocarbon and oxidized to water. For example, 1 mole of butane requires 1 mole of oxygen for the conversion into butadiene, i.e., twice the amount needed to convert butene. In practice, 0.5

. to 1.5 of the theoretical amount of oxygen is preferably 1 used.

The halogen is preferably bromine or iodine. Particularly preferred is iodine. The halogen may be supplied in the form of a suitable halogen-containing compound, which'ca'n yield the elemental halogen under the conditions of the reaction.

e.g., the iodide, or a halohydrocarbon. In the latter case, a halogen derivative of the hydrocarbon to be' dehydro genated is suitably employed, such as butyl iodide in the dehydrogenation of butane. When part of the reaction products are recycled in the process, they will usually contain halogenated products, e.g.,-hydrogen iodide, alkyl iodides, etc.

The amount of halogen which is used may vary within relatively wide limits. Owing to economic considerations, however, it is preferable to use as small an amount of halogen as possible. An important advantage of the present invention is that the dehydrogenation process may be carried out in the presence of only very small amounts of the halogen, which are appreciably lower than would stoichiometrically be required. The halogen therefore ,may be considered as acting merely as a catalyst, and

even traces thereof will in many cases suffice to catalyze the reaction. In such cases, regeneration of the halogen for re-use is not required and may be omitted. Generally, it is preferable to employ the halogen in quantities less than 0.1 mole per mole of the hydrocarbon feed. The

The halogen may thus be formed, for example, from the corresponding hydrogen halide,

- butadiene.

amount of halogen is suitably between 0.001 to 0.09 mole per mole of hydrocarbon, and preferably between 0.01 and 0.06 mole per 'mole of the hydrocarbon. Excellent results have been achieved in the foregoing range when one or two new CC= bonds were introduced into the molecule, as in the conversion of butanes and butenes into When, however, the formation of a larger number of bonds is involved, e.g., in the preparation of benzene from n-hexane, the relative quantities of halogen should be somewhat higher.

The presence of inert diluents, for example, nitrogen or water, in the gaseous feed mixture has often beenfound to have a beneficial effect on the conversion as well as on the selectivity, particularly when dior poly-olefins are to be produced. Very satisfactory results have been obtained by using steam as the diluent. Although the desirable amount of steam depends on the particular hydrocarbon to be dehydrogenated and on the reaction conditions,

the admixture of between 1 and 10 moles of water per mole of the hydrocarbon, and preferably between 2 and 6 moles per mole, is generally referred.

The temperature at which the dehydrogenation is carried out may be between about 375 and 1000 C. It is generally preferable, however, not to exceed 650 C. Temperatures of between about 450 C. and 575 C., and especially between about 475 C. and 525 C., have been found to be very favorable. The reaction is conducted at ordinary pressures, although, if desired, higher 'or lower pressures may be employed.

In practicing the present invenion, the gaseous mixture is passed over the solid catalyst with space velocities which may vary between rataher wide limits. cases, however, space velocities of between 10 and 1000 liters per weight of catalyst per hour, and preferably between 20 and' 100 liters per weight of catalyst per hour, have been found particularly suitable and advantageous. The space velocity is defined as the volumes of hydrocarbon feed at C. and 1 atmosphere which pass through the reactor per hour per unit volume of the catalyst. The surface area of the catalyst is advantageously at least 1 square meter per gram, and generally does not exceed 500 square meters per gram.

It is to be understood that the process may be carried out either by passing the gas mixture over a solid bed of the catalyst, or in a fluidized reactor; such procedure being well understood by those skilled in the art. Particularly favorable results have been obtained through the use of a fluidized reactor. Moreover, the catalytic material may be present entirely or partly in the form of a melt. When in these cases a carrier is used, the pore r diameter may not become too small by the wetting of the inner walls of the pores, as otherwise these would be inaccessible to the reacting gas mixture. I

The catalyst according to the invention is preferably supported on'a carrier. Various materials, such as pumice or ceramic material may be employed, but by far the best results are obtained with alumina and/or silica, e.g., silica gel. The amount of the catalyst present may be very small. Even traces of the compounds in question are sufiicient to catalyze the reaction. Preferably, however, at least 0.80 millimole of the catalyst should be present per gram of the carrier. Excellent results are obtained when 1.0 millimole or more, and particularly at least 1.4 millimoles of the catalyst are present per gram of the carrier. e

The solid catalyst should consist of or contain one'or more alkali metal and/or alkaline-earth metal compounds. Examples are compounds derived from lithium, sodium,

potassium, calcium, strontium or barium. Sodium or-potassium compounds are particularly suitable. Simple compounds are usually preferred, e.g., oxides, hydroxides, I

carbonates, silicatesor sulfates. Very good results have been obtained with halides, particularly bromides. An excellent catalyst is potassium bromide either alone or in admixture with other catalysts and/or promoters. Fur- In most ther examples are potassium chloride and potassium iodide. Frequently, even traces of these compounds are sufficient to catalyze the reaction.

The effect of the solid catalyst is appreciably enhanced if in addition one or more metal compounds derived from the transition elements of Groups I and IV to VIII of the Periodic Table and/or a rareearth metal compound are also present. Good results have been obtained when using compounds such as the oxides or halides. Although the relative amounts of the alkali metals and/or alkalineearth metal compounds(s) and the metal compound(s) of the transition elements of Groups I and IV to VIII and/ or the compound(s) of the rare-earth elements may vary within wide limits, it is advisable to use catalysts wherein the atomic ratio of alkali and/or alkaline-earth metal to transition metal and/or rare-earth metal is not less than v 1 and not more than 7. Catalysts wherein the atomic ratio mentioned above is between 3 and 5 are particularly preferred. Thus, very good results have been obtained when the atomic ratio of an alkali metalz-transition metalzrare-earth metal was 4:1:1.

Examples of elements of the above-mentioned Groups I and IV to VIII which will give beneficial effects are zirconium, titanium, vanadium, chromium, molybdenum,

manganese, tungsten, iron, cobalt, nickel, palladium, cop- The compound used is preferably a brocorresponding didymium chloride is particularly preferred.

A suitable solid catalyst (plus carrier) for the dehydrogenation of butene to butadiene has the following composition (in parts by weight): A1 0 90.2; 'SiO 9.0; Fe O 0.2; MgO 0.1; CaO 0.1; Na O 0.1; K 0 0.1; and TiO 0.2. A catalyst which was successfully used in the dehydrogenation of n-butane contained, in addition, 1.7 didymium oxide, 0.6 Na O, and 1.4 M00 the latter compounds as Na-molybdate. In another similar case, the additional compounds consisted of 11.4 Bi OQ and 7.0 M00 parts by weight. Excellent results were also obtained with a solid catalyst consisting of SiO 19.9 didymium oxide; 17.1 M00 and 3.7 Na O parts by weight.

Preferred catalysts are composed of potassium bromide, silver bromide, and didymium chloride, particularly when supported on a suitable carrier. Much improved conversions and selectivities to butadiene were achieved in all cases as compared with experiments carried out in the absence of a catalyst.

The catalyst which generally consists of a mixture of various components must be brought into a finely subdivided form. This may be effected by any of the known methods, e.g., mixing and grinding. When, however, the catalyst is used on a carrier, as is usually the case, a simple method consists in impregnating the carrier with a solution containing the catalytic material. Frequently catalyst components are used which are insoluble in water. In these cases one may start from the solution of a corresponding pre-catalyst from which the desired catalyst may be precipitated by means of a suitable precipitating agent. The carrier with the supported catalytic material is subsequently dried. In other cases a pre-catalyst is brought on the carrier and converted in situ into the desired compound(s) by treatment with an appropriate reagent, e.g., HBr, and/or by calcination. Thus, a carrier is impregnated with one or more nitrates, and the latter are entirely or partly converted into the corresponding oxides by calcination. Usually the feed mixture used contains active reagents, such as hydrogen iodide, which bring about conversion in situ of the catalytic material TABLE m originally present on the carrier.

The dehydrogenation products obtained according to Total Selectivity the invention are important chermcals which may for exc e l wglvterswn ample be used in the preparation of high polymers. 5 mm m m 2135155 0438 I 1110 EXAMPLES 2.08 KBr-LOQ Dick-0.82 Ag'Br-IOO Prepamlwn the catalyst 6m 36 n 1 The carrier material was calcined at 900 C. during 24 g p 57 8 2 9 72 0 hours before use. It was then impregnated with an aque- 10 2.08 fi in -1.09 Dick-4.02 AgI--1o0 m a 5 8 7 ous solution containing the catalyst or the components 5gffig jbg'igfjgifbpjfifid5,555.15:I 1 0&5 thereof 1n the form of the soluble salt(s). The tmpreg- 1.301(01-100 DiCl;l.02AgI-l00support. 61.8 5.8 66.8 nated carrier was dried first on a steam bath with con- 626 1&3 594 tinuous stirring, and subsequently in a furnace at 550 C. r for 5 hours. Insoluble catalysts were precipitated on the E N E v carrier, e.g., AgNO +HBr AgBr. MMPLTE g g fig gf gfgg zg THE The composition of the catalysts reported in the follow: ing examples is expressed as percent by weight calculated same'l'eactlon Fondltwns were as 111 ExamPle on the carrier. The experiments described in Examples The Gamer mammal was the same as m the foresolng I-VIlI were carried out using a fixed bed reactor. 2 examples- EXAMPLE I.CONVERSION 0F BUTANE 'ro BUTENE Tot 81 S 1 u it e 00 V v AND BUTADIENE 0 mt Mal cogwersion Y 4 on ma u ane A gaseous mixturecontaming butane, an, iodine and percent 04E! 04E steam 1n a molar ratio of 1:4.76:0.04:2.9 was fed over mol various catalysts at a reactor temperature of 500 C. and with a space velocity of 30. The catalyst was supported 130 Km mgmch 102A I 100 i g z a- Suggfirt 61.8 5.5 66.8

1.30 Cl1.09DiCh-0.63 Moos-100 TABLE I supgor 60.2 8.0 67.4

1.30 01-109 mole-1.02 WOl-HX) su ort 58.5 3.2 63.1 T l flelecuvlw 1.30 i Cl-1.09 DiCl -(L53 zro,-100 co verslon su orl; 60.1 9.3 66.4 Contact material butane, .130 c1-1.09 Dick-0.78 Ml1(NO|)r-- Percent 4 4 s 100 su port 52.3 12.0 59.9 Y m 1.30 KC -1.09 Dick-0.80 co(No,),-

1 porgafifdnufiainfifi3 58.5 3.6 70.3 -1. Quartz wool 25.4 41.3 9.1 100 511 ort f: fifljj: 57.9 3.1 72.7 2.08 KBr-IOO alpha-A110: 58. 6 3. 8 66. 7 1.30 KC -1.00 Dick-0.80 Ni(N0;)r- 2.0a KBr-LOQ Dion-100 alpha-A1203 01.1 8.0 67.4 1 05 port 68.5 1.9 68.9 2.08 KBr-ALSZ AgBr-IOO alpha-A1103 55. 7 2. 3 65. 7 130 KCY-LOQ Dick-0,73 Pdcl -mo 2.0a KBr1.09 Dick-0.82 AgBr-100 5 Su ore 56.0 2.0 75.2

port -4. 61.6 3.6 79.1 40 1.30%01-100 Dion-0.50 CuCl -l00 support 58.0 12.1 63.4

p pi effect obtauied when the catalyst Equimolecular amounts of the various transition metal tams in addition to the alkali metal compound both a com d l poun s were tested. compound of a transition element and a rare-earth metal compound. EXAMPLE V.-EFFECT OF THE AMOUNT OF CATALYST PRESENT ON THE CARRIER EXAMPLE II.-Er=rscr 0F IooINE e The same reaction conditions and the same carrier were A gaseous mixture containing butane or butene, air and used as in Example I. steam in a molar ratio of l:4.76:2.9 was used as the 112- r TABLE v actor feed. To this feed iodine vapor was added. The reaction temperature was 500 C. Tom selectivity The catalyst had the following composition: 4.80-KI, Catalyst cogmerslon 0.36 DiCl 3.40 Agl, supported on 100 alpha-M 0 ere...

TABLE II 2.00 KCl-2.18 DlClr-LZB Moor-100 suppo 55.7 3.2 71.1 S M r Total l tiv y 1.30 KCl-1.0e Dick-0.03 Mom-100 sup- Contact Ve ocity ratio eonverport 60.2 8.0 67.4 Feed material of hydro- I2/C4 sum, 04 0.65 KCl-OM mob-0.32 M00;- 100 supcarbon hydro hydro- C-IIIE 0411 part 59.3 9.1 61.7

carbon carbon,

percent EXAMPLE VI.-UsE OF HI FROM Wrncn IODINB 1s GENERATED UNDER THE REACTION Commons 8:31:11: 8 The same reaction conditions and the same carrier 9 g 8 23-2 v 3-} were used as in Example I. The composition of the 1 i" 'j 230 0, 005 15 30:3 catalyst was as follows: 2.60 KCl, 1.26 M00 supported 1-6 It Catalyst-.. 40 0 29.9 81.1 mini .do 40 0.002 91.6 903 on earner TABLE VI Quartz wool alone even gives a conversion, which is ap- I d M l a T t 1 selectivity 0 ['10 ar 0 O 8 C011 6!- preclably higher when starting from butene than from species z i g sum bulge, butane. percent mol 04H. 04H.

EXAMPLE III.I-EFFECT or THE TYPE or HAEIDE I, 6 M M 5 The same reaction conditions and the same carrier ma- HI 4&9

terial were used as in Example I.

EXAMPLE VIL-Erracr OF THE MOLAR RArIo IODINE/BUTANE A gaseous mixture of butane, air, and steam'in a molar ratio of 1:5.84:2 was fed together with iodine over the catalyst at a reactor temperature of 520 C. and with a space velocity of 40. The test was carried out in a continuous run of 120 hours. The catalyst used had the same composition as in Example 11.

TABLE VII Total conver- Selectivity Iodine/butane, sion butane,

molar ratio percent mol ra C4110 EXAMPLE VIIL-CATALYs'r LIFE A gaseous mixture of butane, air, hydrogen iodide and steam in a molar ratioof 1:4.86:0.08:3 was passed over the catalyst at reactor temperatures of 485 C. and 500 C. and with a space velocity of 28.5. The composition of the catalyst was the same as in Example 11.

Dehydrogenations in a fluidized bed reactor The experiments described in Examples IX-XI were carried out using a fluidized bed reactor.

EXAMPLE lX-Convansron or BUTANE T0 BUTENE AND BUTADIENE The catalyst had the following composition: 6.38 KBr, 3.15 AgI, 3.34 DiCl supported on 100 A1 0 The carrier material was a sintered alumina.

The particles of the contract material were held in a fluidized state by passing a gaseous mixture of butane,

oxygen, nitrogen, iodine, and steam through the catalyst bed. The reaction temperature was 525 C. and a space velocity of 80 was used.

TABLE 1X Molar ratio, reactor feed Total eonver- Selectivity sion butane, percent mol C4Hm= 2 2 2= 2 2 01H; CJHQ EXAMPLE X.--CONVERSION or ETHANE 'ro ETHENB The catalyst used had the following composition: 6.38 KBr, 2.52 AgBr, 3.34 DiCl supported on 100 Al O The carrier was the same as in Example IX. The reaction temeprature was 575 C. The other reaction conditions were the same 'as in Example IX.

TABLE X Total conversion ethane, percent mol 85.7 Selectivity, 0 H, 75.7

- Selectivity, cgHz EXAMPLE XI.--CoNvERs1oN or E'I'HYLENE T0 ACETYLENE The same catalyst and the same reaction conditions were used as in Example X, with the exception that the reaction temperature was 800 C.

TABLE XI Total conversion ethylene, percent mol 76.1 27.9

a first hydrocarbon selected from the group consisting of parafiins and olefins to a corresponding less saturated second hydrocarbon, consisting essentially of reacting said first hydrocarbon, in the vapor phase, at a temperature of from about 375 to about 1000 C., with a halogen selected from the group consisting of bromine and iodine, in a mole ratio of said halogen to said first hydrocarbon in the range of from about 0.00121 to about 0.09:1, in the presence of added free oxygen, and of a solid catalyst consisting essentially of an alkali metal halide in combination with from about 1 to about 7 moles of silver halide, and in the additional presence of from about 1 to about 7 moles per mol of said alkali metal halide of at least one member of the group consisting of the oxides and halides of zirconium, titanium, vanadium, chromium, molybdenum, manganese, tungsten, iron, cobalt, nickel, palladium and copper.

2. The process in accordance with claim 1 wherein said solid catalyst is employed in combination with a rare earth metal.

3. The process in accordance with claim 1 wherein said solid catalyst consists of potassium bromide in combination with from about 1 to about 7 moles of silver bromide per mole of said potassium bromide.

4. The process in accordance with claim 3 wherein said process is executed in the additional presence of from about 1 to about 7 moles of didymium chloride per mole of potassium bromide present.

5. The process in accordance with claim 1 wherein said process is executed at temperature of from about 450 to about 575 C.

6. The process in accordance with claim 1 wherein said catalyst is employed in further combination with a catalyst support consisting of at least one member of the group consisting of silica and alumina.

References Cited by the Examiner UNITED STATES PATENTS 2,308,489 1/43 Cass 260-654 2,370,513 2/45 Amos 260-680 2,434,888 1/48 Rust et al 260-604 2,643,269 6/53 Augustine 260-604 2,879,300 3/59 Cheney etal 260-604 2,971,995 2/61 Arganbright 260-683.3 3,028,440 4/62 Arganbright 260-680 3,080,435 3/ 63 Nager 260-680 3,106,590 10/63 Bittner 260-680 3,130,241 4/64 'Baijle et a1. 260-680 OTHER REFERENCES Mocller:- Inorganic Chemistry, John Wiley & Sons, Inc., New York, 1952, pp. 102-106.

ALPHONSO D. SULLIVAN, Primary Examiner.

PAUL M. COUGHLAN, Examiner. 

1. THE PROCESS FOR THE CATALYTIC DEHYDROGENATION OF A FIRST HYDROCARBON SELECTED FROM THE GROUP CONSISTING OF PARAFFINS AND OLEFINS TO A CORRESPONDING LESS SATURATED SECOND HYDROCARBON, CONSISTING ESSENTIALLY OF REACTING SAID FIRST HYDROCARBON, IN THE VAPOR PHASE, AT A TEMPERATURE OF FROM ABOUT 375* TO ABOUT 1000*C., WITH A HALOGEN SELECTED FROM THE GROUP CONSISTING OF BROMINE AND IODINE, IN A MOLE RATIO OF SAID HALOGEN TO SAID FIRST HYDROCARBON IN THE RANGE OF FROM ABOUT 0.001:1 TO ABOUT 0.09:1, IN THE PRESENCE OF ADDED FREE OXYGEN, AND OF A SOLID CATALYST CONSISTING ESSENTIALLY OF AN ALKALI METAL HALIDE IN COMBINATION WITH FROM ABOUT 1 TO ABOUT 7 MOLES OF SILVER HALIDE, AND IN THE ADDITIONAL PRESENCE OF FROM ABOUT 1 TO ABOUT 7 MOLES PER MOL OF SAID ALKALI METAL HALIDE OF AT LEAST ONE MEMBER OF THE GROUP CONSISTING OF THE OXIDES AND HALIDES OF ZIRCONIUM, TITANIUM, VANADIUM, CHROMIUM, MOLYBDEUM, MAGANESE, TUNGSTEN, IRON, COBALT, NICKEL, PALLADIUM AND COPPER. 